Ongoing research at UPMC on the study "Mechanisms of Immune Tolerance in ABPA" has studied people with CF and ABPA versus those patients with CF that just grow A. fumigatus (Af) in the sputum, but do not have ABPA. You may have participated in this study. This study has shown that people with CF with the fungus, Af, in their sputum but who do not have ABPA have more of a certain type of cell in their blood that helps the body to regulate or suppress allergic reactions than those people with CF and ABPA.